The interviewer wants to learn more about who you are as a person. Think about the things that people have repeatedly commended you on, special talents you pride yourself on, and ultimately, the transferable hard or soft skills that are unique to you. Often, having a grounded approach, or some basic leadership skills, can not only improve your professional life, but can also lend a lot to your personal life as well. Share that as well. It will communicate that these merits are intrinsic to your character, and will be consistent in your work performance as well. For example, learning the skills of non-defensive communication can lend quite a lot to your personal relationships as well.